Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1997-01-06
1998-09-01
Willse, David H.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
A61F 236
Patent
active
058005579
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a joint prosthesis, and in particular to a joint prosthesis for a femoral head of a hip joint, which head cooperates with an acetabulum, as well as to a surgical device for making a drilling in at least one joint head.
A joint prosthesis of the type to which this invention is directed is known from the DE 35 38 346 A1. The cap of the known prosthesis is closed, at the bottom side thereof averted from the acetabulum, by a base with which the cap abuts a contact surface milled for this purpose in the femoral head. The fixing of the cap on the femoral head is effected with bone cement which is applied onto the milled contact surface. The cap-side telescopic member of this known prosthesis is a pin guided for free sliding movement in axial direction within a sleeve, which sleeve is fixed to the supporting member. The hold of the cap on the bone system is solely secured by the bone cement. Should this cement bond become loose in the course of time, the cap looses its hold.
The object of the invention is to provide for a joint prosthesis which can be simply, easily, and precisely implanted, which requires only slight, if any, machining of the joint head, like removal of pathological cartilage, and which is reliably protected against loosening even under a prolonged period of use.
This object is achieved by the features of the invention in a surprisingly simple manner.
By making use of the inner surface of the cap as the contact surface for the joint head the milling of a contact surface can be avoided. Veins supplying the joint head will remain preserved. By sparing removal of pathological cartilage the corticalis of the head is preserved what will provide for a solid contact surface for tile cap. The restraining means of the subject invention provides for safe anchoring of the cap in relation to the bone system without the necessity of the cap being cemented to the bone system. Particularly, lifting off of the cap from the joint head is prevented, while spontaneous contraction of the telescopic arrangement under the influence of pushing forces exerted on the cap or of additional tensile force applied by an optionally provided spring, respectively, is possible without any further ado.
The term "cap" presently is intended to also include a segment of a cap
In the case of the prosthesis known from DE 35 38 346 A1 the cap, the telescopic arrangement and the supporting member--except of the pin being sideably guided in the sleeve in longitudinal direction--altogether form a static system causing stiffening of the femoral head and of the neck of the femur with respect to the shaft of the femur. The known prosthesis therefore does not allow for biomechanical motions of the femur head and of the neck of the femur with respect to the shaft of the femur. Because of this there inevitably is a not insignificant osteoclasis of the femur in the area of the femur head and neck of the femur. This can be efficiently prevented, in conformity with a preferred further development of the invention, by a flexible and/or pivotal arrangement of the interconnection allowing for balancing of either pushing or pulling movements of the femoral head and the neck of the femur. Biomechanical motions of the femoral head and of the neck of the femur with respect to the shaft of the femur are thus enabled at least to a partial extent. Pushing, pulling, and shearing forces can therefore e.g. be transmitted by or introduced into the femur, whereby preservation of the bone and even new formation thereof can be reached. It is advisable to choose the elasticity and flexibility of the prosthesis so as to merely dimension or limit the elasticity and flexibility of the prosthesis to an extent excluding any possible risk of breaking of the femoral head or the neck of the femur in the prosthesis area.
Advantageous further developments of the joint prosthesis are the subject of to other aspects of the invention. Thus, hingedly connecting the telescopic arrangement to the supporting member or spring-elastically supporting the teles
REFERENCES:
patent: 4005495 (1977-02-01), Locke et al.
patent: 4274164 (1981-06-01), Rehder
Safran David S.
Willse David H.
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